Score of Parentheses — Stack Depth Doubling

# Python — stack approach
def scoreOfParentheses(s):
    stack = [0]  # start with base score
    for c in s:
        if c == '(':
            stack.append(0)
        else:
            v = stack.pop()
            stack[-1] += max(2*v, 1)  # () -> 1, (A) -> 2*A
    return stack[0]

# Depth approach O(1) space
def scoreOfParentheses(s):
    ans = depth = 0
    for i, c in enumerate(s):
        if c == '(': depth += 1
        else:
            depth -= 1
            if s[i-1] == '(': ans += 1 << depth
    return ans

// Java
public int scoreOfParentheses(String s) {
    Deque<Integer> stack = new ArrayDeque<>();
    stack.push(0);
    for (char c : s.toCharArray()) {
        if (c == '(') stack.push(0);
        else { int v = stack.pop(); stack.push(stack.pop() + Math.max(2*v, 1)); }
    }
    return stack.pop();
}